1.

var a = [1,2,3,5];

console.log(Math.max.apply(null, a));//最大值

console.log(Math.min.apply(null, a));//最小值

2.

var tmp = [1,12,8,5];

var max = tmp[0];

for(var i=1;i<tmp.length;i++){

  if(max<tmp[i])max=tmp[i];

}

console.log(max);